The goal of this project is to improve the clinical performance of amalgam. The approach will be to gather information which can serve as a base for the rational modification of dental amalgam systems. The scientific discipline involved will be essentially metallurgy. Since the performanc3 of a metal alloy is specifically related to its microstructure, the following procedure will be utilized. Microstructural features of existing alloys will be identified and related to relevant laboratory tests which are considered to be most predictive of clinical performance. In addition, methods to modify microstructure will be determined so that optimized configurations can be achieved. Microstructural examination will be performed using microprobe and X-ray diffraction analyses as well as optical metallography. Relevant laboratory tests will include creep, transverse strength, compressive strength, setting dimensional change and anodic polarization. The effects of storage time, temperature and environment on both microstructure and properties will also be studied. In view of the predominant role played by amalgam in the restoration of carious posterior teeth, even minor improvements in this material can produce very significant oral health benefits.